Computer disk drives store information on magnetic disks. Typically, the information is stored on each disk in concentric tracks that are divided into sectors. Information is written to and read from a disk by a transducer that is mounted on an actuator arm capable of moving the transducer radially over the disk. Accordingly, the movement of the actuator arm allows the transducer to access different tracks. The disk is rotated by a spindle motor at high speed which allows the transducer to access different sectors on the disk.
A conventional hard disk drive (HDD) system, generally designated 10, is illustrated in FIG. 1. The HDD system 10 comprises a data storage disk 12 that is rotated by a spin motor 14. The spin motor 14 is mounted to a base plate 16.
The HDD system 10 also includes a drive arm assembly 18, which includes a transducer 20 mounted to a flexure arm 22. As is conventional, the transducer 20 comprises both a write head and a read head. The drive arm assembly 18 is attached to an actuator arm 24 that can rotate about a bearing assembly 26. A drive voice coil motor (VCM) 28 cooperates with the actuator arm 24 and, hence, the drive arm assembly 18, to move the transducer 20 relative to the disk 12.
The spin motor 14, voice coil motor 28 and transducer 20 are coupled to a number of electronic circuits 30. As will be described in further detail below, the electronic circuits 30 typically include a read channel chip, a microprocessor-based controller, a random access memory (RAM) device, and associated signal drive and logic circuitry.
The disk drive system 10 typically includes a plurality of disks 12 and, therefore, a plurality of corresponding actuator arm assemblies 18. However, it is also possible for the disk drive system 10 to include a single disk 12 as shown in FIG. 1. Typically, one drive arm assembly 18 is provided for each surface of each disk 12. If multiple actuator arm assemblies 18 are used, each actuator arm assemblies 18 may be moved separately or two or more actuator arm assemblies 18 may be moved together.
FIG. 2 is a functional block diagram which illustrates a conventional disk drive such as that depicted at 10 in FIG. 1. The example hard disk drive system 10 is coupled to a host device 32 via an input/output port 34. In addition to the components of the disk drive system 10 shown and labeled in FIG. 1, FIG. 2 illustrates (in block diagram form) that the electronic circuits comprise a drive controller 36, a read/write channel 38, and an interface 40. The details of construction and operation of the host device 32, input/output port 34, and/or interface 40 are or may be conventional and will not be described herein in further detail.
The disk drive system 10 is used by the host device 32 as a data storage device. The host device 32 is typically a general purpose computing device but may be any device requiring the storage of data, such as a media playback device, telephone, camera, camcorder, or the like. The host device 32 delivers data access requests to the disk drive system 10 via the input/output port 34. The port 34 is used to transfer data between the disk drive system 10 and the host device 32 during read and write operations.
The drive arm assembly 18 is a semi-rigid member that acts as a support structure for the transducer 20, holding it above the surface of the disk 12. The drive arm assembly 18 is coupled at one end to the transducer 20 and at another end to the drive VCM 28. The drive VCM 28 is operative for imparting controlled motion to the actuator arm 18 to appropriately position the transducer 20 with respect to the disk 12. The drive VCM 28 operates in response to a control signal generated by the drive controller 36. The drive controller 36 generates the control signal in response to, among other things, an access command received from the host device 32 via the interface 40.
The read/write channel 38 is operative for appropriately processing the data being read from/written to the disk 12. For example, during a read operation, the read/write channel 38 converts an analog read signal generated by the transducer 20 into a digital data signal that can be recognized by the drive controller 36. The channel 38 is also generally capable of recovering timing information from the analog read signal.
During a write operation, the read/write channel 38 converts data received from the host device 32 into a write current signal that is delivered to the transducer 20 to “write” the data to an appropriate portion of the disk 12. The read/write channel 38 is also operative for continually processing data read from servo information stored on the disk 12 and delivering the processed data to the drive controller 36 for use in, for example, transducer positioning.
Referring now more specifically to the hard disk 12, as depicted in FIG. 2 data is stored on the disk 12 in substantially concentric data storage tracks 42 on its surface. The example data storage disk 12 also includes servo information in the form of a plurality of radially-aligned servo spokes 44 that each cross all of the tracks 42 on the disk 12. The portions of the track between the servo spokes 44 have traditionally been used to store data received from, for example, the host device 32 and are thus referred to herein as data regions 46.
In a magnetic disk drive system 10, data is stored, for example, in the form of magnetic polarity transitions within each track 42. Data is “read” from the disk 12 by positioning the transducer 20 (i.e., the read head) above a desired track 42 of the disk 12 and sensing the magnetic polarity transitions stored within the track 42 as the disk 12 moves below the transducer 20. Similarly, data is “written” to the disk 12 by positioning the transducer 20 (i.e., the write head) above a desired track 42 and delivering a write current representative of the desired data to the transducer 20 at an appropriate time.
The data storage tracks 42 are illustrated as center lines on the surface of the disk 12; however, it should be understood that the actual tracks will each occupy a finite width about a corresponding centerline. It should be understood that, for ease of illustration, only a small number of tracks 42 and servo spokes 44 have been shown on the surface of the disk 12 of FIG. 3. That is, conventional disk drives include one or more disk surfaces having a considerably larger number of tracks and servo spokes.
The servo information in the servo spokes 44 is a specialized form of data stored on the disk 12 that is read by the transducer 20 during disk drive operation for use in positioning the transducer 20 above a desired track 42 of the disk 12. In particular, the disk drive system 10 operates in at least two positioning modes: seek and track following. During the seek mode, the system 10 moves the transducer 20 from an initial track 42a to a target track 42b. During the track following mode, the system 10 maintains the transducer 20 above the desired track 42 while data is read from or written to the disk 12.
The servo information is configured to allow the system 10 to operate in both the seek and track following modes. In particular, the servo information stored in the servo spokes allows the system 10 to determine a position of the transducer 20 relative to the disk 12. As is well-known in the to art, this position information is used during seek and track following modes by a servo compensator embodied by the drive controller 36.
Referring back for a moment to FIG. 2, it can be seen that the read/write channel comprises a preamplifier circuit 50 and a channel circuit 52. The preamplifier circuit 50 performs two functions. First, the preamplifier circuit 50 generates a write signal for driving the write head portion of the transducer 20 based on an analog differential drive signal generated by the channel circuit 52. Second, the preamplifier 50 generates an analog playback signal based on a read signal generated by the read head portion of the transducer 20. The playback signal is delivered to the channel circuit 52. The channel circuit 52 also performs two basic functions. First, the channel circuit 52 generates the analog differential drive signal based on the digital data to be written to the disk 12. Second, the channel circuit 52 converts the analog playback signal into digital data that can be processed by the drive controller 36 and/or host device 32. The details of construction and operation of the channel circuit 52 are or may be conventional and will not be described herein in further detail.
When the HDD system 10 is initially manufactured, the disk 12 is not formatted. Until the disk 12 is formatted with conventional or spiral servo track information, the drive controller 36 cannot determine the position of the transducer 20 relative to the disk 12. The transducer 20 thus cannot be used to read and write information of any kind, including servo information, to the disk 12 upon initial manufacture of the HDD system 10.
Referring now to FIG. 3 of the drawing, depicted therein is a servo track writer system 60 that is used to write servo track information onto the HDD system 10 immediately after initial manufacture of the system 10. The servo track information allows the disk 12 to be formatted for reading and writing using the drive controller 36.
The example servo track writer (STW) system 60 comprises, in addition to components the HDD system 10, an external controller 62, an external VCM 64, an external arm assembly 66, and a position sensor 68. To form the STW system 60, the disk 12 is mounted in a predetermined spatial relationship with the external VCM 64 and external arm assembly 66. The external arm assembly 66 is then mechanically coupled to the drive arm assembly 18. Under control of a servo compensator embodied by the external controller 62, the external VCM 64 moves the external arm assembly 66, and thus the drive arm assembly 18, to allow servo track information to be written to the disk 12.
After the servo track information has been written to the disk 12, the HDD system 10 is removed from the STW system 60. At that point, the disk 12 contains sufficient servo track information to allow the formatting process may be completed, if necessary, using the drive controller 36.
Ideally, the mechanical coupling between the external arm assembly 66 and the drive arm assembly 18 is absolutely rigid. In practice, however, it is not possible to ensure an absolutely rigid mechanical connection between the drive arm assembly 18 and the external arm assembly 66.
In particular, the mechanical connection between the arm assemblies 18 and 66 is formed by a pushpin 70 that extends from the external arm assembly 66 and a pushpin hole 72 (also shown in FIG. 1) formed in the flexure arm 22 of the drive arm assembly 18. Typically, a pushpin sleeve 74 extends at least partly around an engaging end 76 of the pushpin 70. To form the mechanical connection between the external arm assembly 66 and the drive arm assembly 18, the pushpin 70 is displaced, typically through an opening in the housing (not shown) of the HDD system 10, such that the pushpin 70 enters the pushpin hole 72. As shown in FIG. 3, the pushpin sleeve 74 lies between the engaging end 76 of the pushpin 70 and the surface of the flexure arm 22 defining the pushpin hole 72.
With the pushpin 70 in engagement with the drive arm assembly 18, a dominant mechanical pushpin resonance of the system formed by the HDD system 10 and the STW system 60 may appear that is not present in the external VCM dynamics alone. Pushpin resonance plays a major role in the quality of conventional or spiral servo track writing and can be highly influenced by the mechanical pushpin design and pushpin material. If the pushpin resonance occurs at an undesirable frequency or if it is lightly damped, the STW system may oscillate and the resonance frequency may be written into the servo pattern.
The need thus exists for systems and methods for detecting and/or compensating for push pin resonance to modify STW systems and thereby improve the pattern of the servo track information written onto the hard disks by servo track writer systems.